Hi Ashley, I am fully agree with your first paragraph about orchestration.
I understand your second paragraph about choreography but see a conflict in between this concept and SO Principles. Nothing more. Out of this, I am trying to find a business case where choreography would be more preferable than orchestration in SOA, i.e. where me must violate SO Principles to have choreograph-based solution. If we deal with stand-alone self-contained autonomous services, then any idea about their collaboration is the external ised with regard to them. Thus, instead of modifying the services by embedding the knowledge about other services for the collaboration, I can easier (I think) create a new service to play an orchestration manager (conductor) role. Overall, it is not about choreography per se, it's about a mismatch between SOA and choreography (I know how unusual this sounds). - Michael ----- Original Message ---- From: Ashley at Metamaxim <[EMAIL PROTECTED]> To: [email protected] Sent: Monday, September 8, 2008 4:47:09 PM Subject: Re: [service-orientated-architecture] Re: Distinction between "Choreography" and "Orchestration" Hi Michael On the issue of "statelessness" : It seems to me that if multiple participants (P1, P2, P3, ..) are engaged in a collaboration but only one of them (say P1) holds a state, then the situation is one of "Orchestration" rather than "Choreography" . Only P1 can determine or impose any ordering on events in the collaboration, because such determination/ imposition requires the maintenance of state. P1 "orchestrates" the collaboration and the other participants are "slaves": they are invoked to provide some service but, as they have no state, "forget" they that have done it once they have done their job. "Choreography" comes into play when state is held by multiple participants and they all have their own sequencing rules/constraints. Choreogrpahy is about managing the collaboration in such a way that all their constraints are obeyed but without one distinguished orchestrator. In other words, it is peer-to-peer between stateful participants. Rgds Ashley
